%% The MIT License
%% 
%% Paralog is licensed under the MIT License.
%% 
%% Copyright (c) 2008 Robert Ahrens <mindangels@yahoo.com>
%% 
%% Permission is hereby granted, free of charge, to any person obtaining a copy
%% of this software and associated documentation files (the "Software"), to deal
%% in the Software without restriction, including without limitation the rights
%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
%% copies of the Software, and to permit persons to whom the Software is
%% furnished to do so, subject to the following conditions:
%% 
%% The above copyright notice and this permission notice shall be included in
%% all copies or substantial portions of the Software.
%% 
%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
%% THE SOFTWARE.
%% 

%% @author Robert Ahrens <mindangels@yahoo.com>
-module(paralog).

-export([
         pli/2,
         test1/0,
         assume_interpreter/0,
         proc_interpreter/0,
         set_interpreter/1,
         ensure_interpreter/2
        ]).


-define(PLI, '__PROCESS_PARALOG_INTERPRETER__').


test1() ->
    pli(ets_kb, [dartmouth]).


pli(DBMod, ModList) ->
    DB = init_db(DBMod),
    PLI = pl_interpreter:new(DB, []),
    PLI:load_list(ModList).


init_db(list_db) ->
    list_db:new([]);
init_db(gs_kb) ->
    gs_kb_server:start_new();
init_db(ets_kb) ->
    ets_kb_server:start_new().


proc_interpreter() ->
    get(?PLI).


set_interpreter(Interpreter) ->
    Interpreter:assert_type(pl_interpreter),
    put(?PLI, Interpreter).


ensure_interpreter(DBMod, ModList) ->
    case proc_interpreter() of
        undefined ->
            NewPLI = pli(DBMod, ModList),
            set_interpreter(NewPLI),
            NewPLI;
         ExistingPLI ->
            ExistingPLI
    end.


assume_interpreter() ->
    case proc_interpreter() of
        undefined ->
            throw({paralog_error, no_interpreter});
        PLI ->
            PLI
    end.
          


